1. Field of the Invention
This invention relates to telecommunications and more particularly to a switch utilized in a telecommunications network.
2. Description of the Related Art
Communications between different networks using various encoding techniques and multiplexing strategies has led to the development of a number of different switching technologies. These switching technologies are capable of receiving a signal composed of multiple embedded signals, and routing each individual embedded signal to different locations. For example, a common transmission protocol is the synchronous optical network protocol (SONET) specified by the American National Standards Institute (ANSI). SONET allows multiple data streams of different formats to be combined into a single high speed fiber optic synchronous data stream. Current switching technology breaks the SONET signal into its constituent parts, including the separate data streams. The separate data streams are routed appropriately, and then re-assembled into new SONET signals for further transmission.
Generally, the communication switches used in such applications are cross-connect switches employing time-space-time switching. These cross-connect switches receive multiple system inputs that are not frame aligned, and are possibly asynchronous to each other. The communication switch synchronizes and column aligns the inputs using a technique known as pointer processing (the first time component). The column aligned data are then stored in a large central memory (the space component), from which the correct data is selected to create a framed data signal (the second time component). Some other switches employ an elastic memory buffer, which can reduce the need for a large central memory.
Regardless of which type of switch is employed, it is often inconvenient to add functionality to conventional switches. Implementing trans-multiplexing functions in conventional switches (i.e. functions allowing access to additional levels of data channels embedded within embedded data streams), for example, usually requires either a multi-stage switch or multiple passes through a single stage switch. Adding other functionality to conventional switches, for example, redundancy or other protective functions, can require adding both redundant switch elements and extra communication/routing elements.